however, the median transaction fee drastically drops as a result, and in a continued attack soon you could see that ~10% of transactions pay more than the median fee.
And if we use:
% of transactions with a fee higher than (median transaction fee of transactions with a fee)
This excludes zero fee transactions in the calculation of the median transaction fee.
In that case a large quantity of zero fee transactions (and spam) does not have influence on the median transaction fee.